1. Field of the Invention
The present invention relates to an epoxy resin composition having a surface on which minute protrusions can be formed simply by thermosetting the resin composition. The composition is useful as an interlayer insulation material in a multilayer printed-wiring board of the build-up type consisting of alternate layers of conductor circuitry and insulating materials. The present invention also relates to a multilayer printed-wiring board containing the epoxy resin composition and to a process for manufacturing the same.
2. Discussion of the Background
One process which has been used for manufacturing multilayer printed-wiring boards comprises laminating copper foils onto an internal-layer circuit board having a circuit formed thereon, by using several prepreg sheets as insulating bonding layers. Each prepreg sheet is prepared by impregnating glass cloth with an epoxy resin and curing it to a B-stage. Interlayer continuity is achieved by through holes in an external layer. This process suffers from several disadvantages including high cost incurred by large-scale equipment and long production times required for molding the copper foils under heat and pressure using a laminating press. Also, the formation of a fine pattern is made difficult by an increased copper thickness due to the through-hole plating on the external layer.
Attention has recently been drawn as a means for solving these problems, to a technique in which organic insulating layers are formed alternately on conductor layers of an internal-layer circuit board for use in a multilayer printed-wiring board of the build-up type. Japanese Patent Applications Laid-Open Nos. Hei 7-304931 and Hei 7-304933 disclose a process for manufacturing a multilayer printed-wiring board by coating an internal-layer circuit board having a circuit formed thereon with an epoxy resin composition, curing it under heat, forming an uneven roughened surface thereon with a roughening agent and forming conductor layers by plating. Japanese Patent Application Laid-Open No. Hei 8-64960 discloses a process for manufacturing a multilayer printed-wiring board by applying an undercoat adhesive, preliminarily drying it, bonding an additive adhesive in film form thereto, curing it under heat, roughening it with an alkaline oxidizing agent and forming conductor layers by plating. All of these processes have the drawback of being low in productivity, since they have many time consuming steps requiring strict processing controls, including not only the prolonged step of roughening with an oxidizing agent, but also preparatory steps such as mechanical polishing and chemical swelling.